Zoom optical system, optical apparatus and method for manufacturing the zoom optical system

ABSTRACT

A zoom optical system comprises, in order from an object: a first lens group (G 1 ) having positive refractive power; a second lens group (G 2 ) having negative refractive power; and a subsequent group (GR) having at least one lens group. Upon zooming, distances between the first lens group (G 1 ) and the second lens group (G 2 ) and between the second lens group (G 2 ) and the subsequent group (GR) change. The subsequent group (GR) comprises a focusing group (Gfc) having negative refractive power for focusing. The first lens group (G 1 ) comprises a 1-1st lens having positive refractive power and is disposed closest to the object. A following conditional expression is satisfied: 
       0.85&lt; n 1 P/n 1 N &lt;1.00         where,   n1P denotes a refractive index of a lens with largest positive refractive power in the first lens group, and   n1N denotes a refractive index of a lens with largest negative refractive power in the first lens group.

TECHNICAL FIELD

The present invention relates to a zoom optical system, an opticalapparatus using the same and a method for manufacturing the zoom opticalsystem.

TECHNICAL BACKGROUND

A zoom optical system suitable for photographic cameras, electronicstill cameras, video cameras, and the like has conventionally beenproposed (see, for example, Patent Document 1). Optical performance ofsuch a conventional zoom optical system has been insufficient.

PRIOR ARTS LIST Patent Document

Patent Document 1: Japanese Laid-Open Patent Publication No. H4-293007(A)

SUMMARY OF THE INVENTION

A zoom optical system according to the present invention comprises, inorder from an object: a first lens group having positive refractivepower; a second lens group having negative refractive power; and asubsequent group including at least one lens group. Upon zooming,distances between the first lens group and the second lens group andbetween the second lens group and the subsequent group change. Thesubsequent group comprises a focusing group having negative refractivepower for focusing. The first lens group comprises a 1-1st lens havingpositive refractive power and is disposed closest to the object. Afollowing conditional expression is satisfied:

0.85<n1P/n1N<1.00

where,

n1P denotes a refractive index of a lens with largest positiverefractive power in the first lens group, and

n1N denotes a refractive index of a lens with largest negativerefractive power in the first lens group.

An optical apparatus according to the present invention comprises thezoom optical system described above.

A method for manufacturing a zoom optical system according to thepresent invention is a method for manufacturing a zoom optical systemcomprising, in order from an object: a first lens group having positiverefractive power; a second lens group having negative refractive power;and a subsequent group including at least one lens group, the methodcomprising a step of arranging the lens groups in a lens barrel so that:upon zooming, distances between the first lens group and the second lensgroup and between the second lens group and the subsequent group change,the subsequent group comprises a focusing group having negativerefractive power for focusing, the first lens group comprises a 1-1stlens having positive refractive power and is disposed closest to theobject in the first lens group, and a following conditional expressionis satisfied:

0.85<n1P/n1N<1.00

where,

n1P denotes a refractive index of a lens with largest positiverefractive power in the first lens group, and

n1N denotes a refractive index of a lens with largest negativerefractive power in the first lens group.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a lens configuration of a zoom opticalsystem according to Example 1 of the present embodiment.

FIGS. 2A, 2B, and 2C are graphs showing various aberrations of the zoomoptical system according to Example 1 upon focusing on infinity,respectively in a wide angle end state, an intermediate focal lengthstate, and a telephoto end state.

FIGS. 3A, 3B, and 3C are graphs showing various aberrations of the zoomoptical system according to Example 1 upon focusing on a short distantobject, respectively in the wide angle end state, the intermediate focallength state, and the telephoto end state.

FIG. 4 is a diagram illustrating a lens configuration of a zoom opticalsystem according to Example 2 of the present embodiment.

FIGS. 5A, 5B, and 5C are graphs showing various aberrations of the zoomoptical system according to Example 2 upon focusing on infinity,respectively in the wide angle end state, the intermediate focal lengthstate, and the telephoto end state.

FIGS. 6A, 6B, and 6C are graphs showing various aberrations of the zoomoptical system according to Example 2 upon focusing on a short distantobject, respectively in the wide angle end state, the intermediate focallength state, and the telephoto end state.

FIG. 7 is a diagram illustrating a lens configuration of a zoom opticalsystem according to Example 3 of the present embodiment.

FIGS. 8A, 8B, and 8C are graphs showing various aberrations of the zoomoptical system according to Example 3 upon focusing on infinity,respectively in the wide angle end state, the intermediate focal lengthstate, and the telephoto end state.

FIGS. 9A, 9B, and 9C are graphs showing various aberrations of the zoomoptical system according to Example 3 upon focusing on a short distantobject, respectively in the wide angle end state, the intermediate focallength state, and the telephoto end state.

FIG. 10 is a diagram illustrating a lens configuration of a zoom opticalsystem according to Example 4 of the present embodiment.

FIGS. 11A, 11B, and 11C are graphs showing various aberrations of thezoom optical system according to Example 4 upon focusing on infinity,respectively in the wide angle end state, the intermediate focal lengthstate, and the telephoto end state.

FIGS. 12A, 12B, and 12C are graphs showing various aberrations of thezoom optical system according to Example 4 upon focusing on a shortdistant object, respectively in the wide angle end state, theintermediate focal length state, and the telephoto end state.

FIG. 13 is a diagram illustrating a configuration of a camera includingthe zoom optical system according to the present embodiment.

FIG. 14 is a flowchart illustrating a method for manufacturing the zoomoptical system according to the present embodiment.

DESCRIPTION OF THE EMBODIMENTS

A zoom optical system and an optical apparatus according to the presentembodiment are described below with reference to the drawings. Asillustrated in FIG. 1, a zoom optical system ZL(1) as an example of azoom optical system ZL according to the present embodiment includes, inorder from an object: a first lens group G1 having positive refractivepower; a second lens group G2 having negative refractive power; and asubsequent group GR (third lens group G3) including at least one lensgroup. Upon zooming, distances between the first lens group G1 and thesecond lens group G2 and between the second lens group G2 and thesubsequent group GR change. The subsequent group GR includes a focusinggroup Gfc having negative refractive power for focusing (moves uponfocusing on a short distant object from an infinite distant object). Thefirst lens group G1 includes a 1-1st lens L11 that has positiverefractive power and is disposed closest to the object. The focusinggroup Gfc includes at least one lens having positive refractive powerand at least one lens having negative refractive power. The third lensgroup G3 has positive refractive power.

The zoom optical system ZL according to the present embodiment may alsobe a zoom optical system ZL(2) illustrated in FIG. 4, a zoom opticalsystem ZL(3) illustrated in FIG. 7, or a zoom optical system ZL(4)illustrated in FIG. 10. The zoom optical system ZL(2) includes the firstlens group G1, the second lens group G2, and the subsequent group GRconsisting of the third lens group G3, as in the case of the zoomoptical system ZL(1). The zoom optical systems ZL(3) and ZL(4) eachinclude the subsequent group GR consisting of the third lens group G3, afourth lens group G4, and a fifth lens group G5.

The zoom optical system ZL according to the present embodiment includesat least three lens groups, and the distances among the lens groupschange upon zooming from a wide angle end state to a telephoto endstate. Thus, successful aberration correction can be achieved uponzooming. The subsequent group GR includes at least one lens group, andpreferably has positive refractive power as a whole. Examples of theconfiguration of the lens group forming the subsequent group GR includesa configuration consisting of a third lens group having positiverefractive power; a configuration consisting of a third lens grouphaving positive refractive power, a fourth lens group having negativerefractive power, and a fifth lens group having positive refractivepower; and a configuration consisting of a third lens group havingnegative refractive power, a fourth lens group having positiverefractive power, a fifth lens group having negative refractive power,and a sixth lens group having positive refractive power. The distanceamong the lens groups forming the subsequent group GR changes at leastupon zooming. The focusing group Gfc is disposed in the subsequent groupGR, and thus can be small and light weight. When the focusing group Gfcis disposed in the subsequent group GR, the focusing group Gfcpreferably includes a lens disposed to an object side of the focusinggroup Gfc and a lens disposed to an image side of the focusing groupGfc.

With the 1-1st lens L11 having positive refractive power and beingdisposed closest to the object in the first lens group G1, a sphericalaberration in a telephoto end state can be successfully corrected. The1-1st lens L11 may be a single lens or may be cemented with another lensto be a part of a cemented lens.

The zoom optical system ZL according to the present embodiment havingthe configuration described above preferably satisfies the followingconditional expression (1).

0.85<n1P/n1N<1.00   (1)

where,

n1P denotes a refractive index of a lens with largest positiverefractive power in the first lens group, and

n1N denotes a refractive index of a lens with largest negativerefractive power in the first lens group.

The conditional expression (1) is for defining an appropriate range of aratio between the refractive indices of the lens with the largestpositive refractive power and the lens with the largest negativerefractive power in the first lens group G1. Various aberrationsincluding the spherical aberration can be successfully corrected whenthe conditional expression (1) is satisfied. The lens with the largestpositive refractive power and the lens with the largest negativerefractive power in the first lens group G1 are preferably cemented.However, the configuration is not limited to this.

A value higher than the upper limit value of the conditional expression(1) of the zoom optical system according to the present embodiment leadsto small refractive power of the lens with the largest negativerefractive power in the first lens group, rendering various aberrationsincluding the spherical aberration difficult to correct. The effects ofthe present embodiment can be more effectively guaranteed with the upperlimit value of the conditional expression (1) set to be 0.98. To moreeffectively guarantee the effects of the present embodiment, the upperlimit value of the conditional expression (1) is preferably set to be0.96.

A value lower than the lower limit value of the conditional expression(1) of the zoom optical system according to the present embodiment leadsto small refractive power of the lens with the largest positiverefractive power in the first lens group, rendering in an largespherical aberrations that is difficult to correct. The effects of thepresent embodiment can be more effectively guaranteed with the lowerlimit value of the conditional expression (1) set to be 0.87. To moreeffectively guarantee the effects of the present embodiment, the lowerlimit value of the conditional expression (1) is preferably set to be0.89.

The zoom optical system according to the present embodiment preferablysatisfies the following conditional expression (2).

4.30<f1/(−f2)<5.00  (2)

where,

f1 denotes a focal length of the first lens group G1, and

f2 denotes a focal length of the second lens group G2.

The conditional expression (2) is for setting an appropriate range of aratio between the focal lengths of the first lens group G1 and thesecond lens group G2. Variation of various aberrations including thespherical aberration can be prevented upon zooming when the conditionalexpression (2) is satisfied.

A value higher than the upper limit value of the conditional expression(2) leads to large refractive power of the second lens group G2,rendering various aberrations including the spherical aberrationdifficult to correct. The effects of the present embodiment can be moreeffectively guaranteed with the upper limit value of the conditionalexpression (2) set to be 4.95. To more effectively guarantee the effectsof the present embodiment, the upper limit value of the conditionalexpression (2) is preferably set to be 4.90.

A value lower than the lower limit value of the conditional expression(2) leads to large refractive power of the first lens group G1,rendering various aberrations including the spherical aberrationdifficult to correct. The effects of the present embodiment can be moreeffectively guaranteed with the lower limit value of the conditionalexpression (2) set to be 4.35. To more effectively guarantee the effectsof the present embodiment, the lower limit value of the conditionalexpression (2) is preferably set to be 4.40.

The zoom optical system according to the present embodiment preferablyhas a configuration in which the first lens group G1 moves toward theobject upon zooming from a wide angle end state to the telephoto endstate. With this configuration, a short total length of the lenses inthe wide angle end state can be achieved, whereby a small size of thezoom optical system can be achieved.

The zoom optical system according to the present embodiment preferablyhas a configuration in which the first lens group moves toward theobject upon zooming from a wide angle end state to the telephoto endstate. With this configuration, a short total length of the lenses inthe wide angle end state can be achieved, whereby a small size of thezoom optical system can be achieved.

The zoom optical system according to the present embodiment preferablyincludes the focusing group including at least one lens having positiverefractive power and at least one lens having negative refractive power.With this configuration, variation of various aberrations including thespherical aberration can be prevented upon focusing on a short distantobject from an infinite distant object. Preferably, the focusing groupGfc includes three or less lenses. However, this should not be construedin a limiting sense.

The zoom optical system according to the present embodiment preferablysatisfies the following conditional expression (3).

1.00<nFP/nFN<1.20   (3)

where,

nFP denotes a refractive index of a lens with the largest positiverefractive power in the focusing group Gfc, and

nFN denotes a refractive index of a lens with the largest negativerefractive power in the focusing group Gfc.

The conditional expression (3) is for defining an appropriate range of aratio between the refractive indices of the lens with the largestpositive refractive power and the lens with the largest negativerefractive power in the focusing group Gfc. Variation of variousaberrations including the spherical aberration can be prevented uponfocusing when the conditional expression (3) is satisfied.

A value higher than the upper limit value of the conditional expression(3) leads to small refractive index of the lens with the largestnegative refractive power, resulting in extremely large variousaberrations including the spherical aberration upon focusing that aredifficult to correct. The effects of the present embodiment can be moreeffectively guaranteed with the upper limit value of the conditionalexpression (3) set to be 1.18. To more effectively guarantee the effectsof the present embodiment, the upper limit value of the conditionalexpression (3) is preferably set to be 1.13.

A value lower than the lower limit value of the conditional expression(3) leads to small refractive index of the lens with the largestpositive refractive power, rendering variation of various aberrationsincluding the spherical aberration upon focusing difficult to correct.The effects of the present embodiment can be more effectively guaranteedwith the lower limit value of the conditional expression (3) set to be1.01. To more effectively guarantee the effects of the presentembodiment, the lower limit value of the conditional expression (3) ispreferably set to be 1.02.

The zoom optical system according to the present embodiment preferablysatisfies the following conditional expression (4).

0.52<νFP/νFN<0.82  (4)

where,

vFP denotes an Abbe number of the lens with the largest positiverefractive power in the focusing group Gfc, and

vFN denotes an Abbe number of the lens with the largest negativerefractive power in the focusing group Gfc.

The conditional expression (4) is for defining an appropriate range of aratio between the Abbe number of the lens with the largest positiverefractive power and the Abbe number of the lens with the largestnegative refractive power in the focusing group Gfc. Variation of achromatic aberration can be prevented upon focusing when the conditionalexpression (4) is satisfied.

A value higher than the upper limit value of the conditional expression(4) leads to a small Abbe number of the lens with the largest negativerefractive power, resulting in an extremely large chromatic aberrationupon focusing that is difficult to correct. The effects of the presentembodiment can be more effectively guaranteed with the upper limit valueof the conditional expression (4) set to be 0.80. To more effectivelyguarantee the effects of the present embodiment, the upper limit valueof the conditional expression (4) is preferably set to be 0.78.

A value lower than the lower limit value of the conditional expression(4) leads to a small Abbe number of the lens with the largest positiverefractive power, rendering variation of the chromatic aberration uponfocusing difficult to correct. The effects of the present embodiment canbe more effectively guaranteed with the lower limit value of theconditional expression (4) set to be 0.54. To more effectively guaranteethe effects of the present embodiment, the lower limit value of theconditional expression (4) is preferably set to be 0.56.

The zoom optical system according to the present embodiment preferablyincludes the first lens group G1 including, in order from an object: the1-1st lens having positive refractive power; a 1-2nd lens havingnegative refractive power; and a 1-3rd lens having positive refractivepower. With this configuration, the spherical aberration and thechromatic aberration can be successfully corrected.

The zoom optical system according to the present embodiment preferablyincludes the second lens group G2 including, in order from an object: a2-1st lens having negative refractive power; a 2-2nd lens havingpositive refractive power; and a 2-3rd lens having negative refractivepower. With this configuration, various aberrations including thespherical aberration can be successfully corrected.

The optical apparatus according to the present embodiment includes thezoom optical system with the configuration described above. A camera(optical apparatus) including the zoom optical system ZL is described,as a specific example, with reference to FIG. 13. This camera 1 is adigital camera including the zoom optical system according to thepresent embodiment serving as an imaging lens 2 as illustrated in FIG.13. In the camera 1, the imaging lens 2 collects light from an object(subject) (not illustrated), and then the light reaches an image sensor3. Thus, an image based on the light from the subject is formed with theimage sensor 3 to be stored as a subject image in a memory (notillustrated). In this manner, the photographer can capture an image ofthe subject with the camera 1. The camera may be a mirrorless camera, ormay be a single lens reflex camera having a quick return mirror.

With the configuration described above, the camera 1 including the zoomoptical system ZL serving as the imaging lens 2 can have a focus lensgroup that is small and light weight, and thus quick and silent AF canbe achieved without using a large barrel. Furthermore, with thisconfiguration, variation of aberrations upon zooming from the wide angleend state to the telephoto end state, as well as variation ofaberrations upon focusing can be successfully prevented, wherebyexcellent optical performance can be implemented.

Next, a method for manufacturing the zoom optical system ZL describedabove is described with reference to FIG. 14. First of all, the firstlens group G1 having positive refractive power, the second lens group G2having negative refractive power, and the subsequent group GR includingat least one lens group are disposed in the barrel in order from theobject (step ST1). The lens groups are configured in such a manner thatupon zooming, the distances between the first lens group G1 and thesecond lens group G2 and between the second lens group G2 and thesubsequent group GR change (step ST2). The focusing group Gfc havingnegative refractive power for focusing is provided in the subsequentgroup GR and the 1-1st lens L11 that has positive refractive power andis disposed closest to the object is provided in the first lens group G1(step ST3). The lenses are arranged in the lens barrel in such a mannerthat at least the conditional expression (1) described above issatisfied (step ST4).

EXAMPLES

Zoom optical systems (zoom lenses) ZL according to Examples of thepresent embodiment are described below with reference to the drawings.FIG. 1, FIG. 4, FIG. 7, and FIG. 10 are cross-sectional viewsillustrating configurations and refractive power distributions of thezoom optical systems ZL{ZL(1) to ZL(4)} according to Examples 1 to 4. Inthe lower portion of each cross-sectional view of the zoom opticalsystems ZL(1) to ZL(4), the directions in which the lens groups aremoved along the optical axis upon zooming from the wide angle end state(W) to the telephoto end state (T) are shown by arrows. A direction inwhich the focusing group Gfc moves upon focusing on a short distantobject from infinity is shown by an arrow appended with “focusing”.

In FIGS. 1, 4, 7, and 10, a combination of a sign G and a numberrepresents each lens group, and a combination of a sign L and a numberrepresents each lens. In each Example, lens groups and the like are eachdenoted with a combination of the reference sign and numeralindependently from other Examples to prevent cumbersomeness due to anexcessively wide variety or a large number of signs and numerals. Thus,components in different Examples denoted with the same combination ofreference sign and numeral does not necessarily have the sameconfiguration.

Table 1 to Table 20 include Table 1 to Table 5 that are specificationtables of Example 1, Table 6 to Table 10 that are specification tablesof Example 2, Table 11 to Table 15 that are specification tables ofExample 3, and Table 16 to Table 20 that are specification tables ofExample 4. In Examples, d-line (wavelength 587.562 nm) and g-line(wavelength 435.835 nm) are selected as calculation targets of theaberration characteristics.

In Table [Lens specifications], a surface number represents an order ofan optical surface from the object side in a traveling direction of alight beam, R represents a radius of curvature of each optical surface(with a surface having the center of curvature position on the imageside provided with a positive value), D represents a distance betweeneach optical surface and the next optical surface (or the image surface)on the optical axis, nd represents a refractive index of a material ofan optical member with respect to the d-line, and vd represents an Abbenumber of the material of the optical member based on the d-line. In thetable, object surface represents an object surface, “∞” of the radius ofcurvature represents a plane or an aperture, (stop S) represents theaperture stop S, and image surface represents an image surface I. Therefractive index nd=1.00000 of air is omitted.

Specifically, in Table [Various data], f represents a focal length ofthe whole zoom lens, FNO represents F number, 2ω represents an angle ofview (ω represents a half angle of view (unit: °)), and Ymax representsthe maximum image height. Back focus (BF) represents a distance betweena lens last surface and the image surface I on the optical axis uponfocusing on infinity, and TL represents a distance obtained by adding BFto a distance between a lens forefront surface and a lens last surfaceon the optical axis upon focusing on infinity. These values are providedfor each of the zooming states including the wide angle end state (W),the intermediate focal length (M), and the telephoto end state (T).

Table [Variable distance data] includes surface distances d5, d10, d21,and d24 corresponding to surfaces corresponding to surface numbers 5,10, 21, and 24 appended with “variable” in Table [Lens specifications]and the next surface. The surface distances d5, d10, d21, and d24 areprovided for each of the zooming states including the wide angle endstate (W), the intermediate focal length (M), and the telephoto endstate (T) upon focusing on infinity and upon focusing on a short distantobject.

Table [Lens group data] includes the group starting surface (surfaceclosest to the object) and the focal length of each of the first to thethird lens groups.

Table [Conditional expression corresponding value] includes valuescorresponding to the conditional expressions (1) to (4).

The focal length f, the radius of curvature R, the surface distance Dand the other units of length described below as all the specificationvalues, which are generally described with “mm” unless otherwise notedshould not be construed in a limiting sense because the optical systemproportionally expanded or reduced can have a similar or the sameoptical performance.

The description on the tables described above commonly applies to allExamples, and thus will not be redundantly given below.

Example 1

Example 1 is described with reference to FIG. 1, FIGS. 2A-2C, and FIGS.3A-3C and Table 1 to Table 5. FIG. 1 is a diagram illustrating a lensconfiguration of a zoom optical system according to Example 1 of thepresent embodiment. The zoom optical system ZL(1) according to Example 1consists of, in order from an object: a first lens group G1 havingpositive refractive power; a second lens group G2 having negativerefractive power; and a third lens group G3 having positive refractivepower. In this Example, the third lens group G3 forms the subsequentgroup GR. A sign (+) or (−) provided to a sign of each lens grouprepresents refractive power of the lens group. The same applies to allof Examples described below. The aperture stop S is provided in thethird lens group G3, and the image surface I is disposed to the imageside of the third lens group G3.

The first lens group G1 consists of, in order from the object, apositive lens L11 having a biconvex shape and a cemented positive lensconsisting of a negative meniscus lens L12 having a convex surfacefacing the object and a positive meniscus lens L13 having a convexsurface facing the object.

The second lens group G2 consists of, in order from the object, acemented negative lens consisting of a negative lens L21 having abiconcave shape and a positive meniscus lens L22 having a convex surfacefacing the object and a negative lens L23 having a biconcave shape.

The third lens group G3 consists of, in order from the object, apositive lens L31 having a biconvex shape, the aperture stop S, acemented positive lens consisting of a positive lens L32 having abiconvex shape and a negative lens L33 having a biconcave shape, acemented positive lens consisting of a negative meniscus lens L34 havinga convex surface facing the object and a positive lens L35 having abiconvex shape, a positive meniscus lens L36 having a convex surfacefacing the object, a cemented negative lens consisting of a positivemeniscus lens L37 having a concave surface facing the object and anegative lens L38 having a biconcave shape, and a positive lens L39having a biconvex shape.

In the optical system according to Example 1, the cemented negative lensconsisting of the positive meniscus lens L37 and the negative lens L38in the third lens group G3 (subsequent group GR) moves toward the imagesurface upon focusing from a long distant object to a short distantobject. In this Example, the second lens group G2 preferably serves as avibration-proof lens group, with a displacement component in a directionorthogonal to the optical axis, to be in charge of image blur correctionon the image surface I (image stabilization, camera shake correction).

Table 1 to Table 5 below list specification values of the optical systemaccording to Example 1.

TABLE 1 [Lens specifications] Surface number R D nd νd Object surface ∞1 91.1552 6.167 1.51680 63.88 2 −844.6033 0.204 3 92.5357 1.500 1.6476933.73 4 45.6802 6.598 1.48749 70.31 5 154.0927 Variable 6 −211.47951.000 1.69680 55.52 7 22.5821 3.677 1.80518 25.45 8 60.3602 2.652 9−46.9021 1.000 1.77250 49.62 10 299.7358 Variable 11 48.8916 3.7961.69680 55.52 12 −131.4333 1.000 13 ∞ 1.000 (Aperture stop S) 14 39.87994.932 1.69680 55.52 15 −49.6069 1.000 1.85026 32.35 16 72.3703 8.805 1757.3477 1.000 1.80100 34.92 18 18.1075 6.038 1.48749 70.31 19 −116.15860.200 20 26.5494 3.513 1.62004 36.40 21 96.5593 Variable 22 −119.70213.510 1.74950 35.25 23 −16.6839 1.000 1.69680 55.52 24 25.6230 Variable25 124.9308 2.143 1.48749 70.31 26 −480.8453 BF Image surface ∞

TABLE 2 [Various data] Zooming rate 4.12 W M T f 71.4 100.0 294.0 FNO4.56 4.26 5.89 2ω 22.82 16.04 5.46 Ymax 14.25 14.25 14.25 TL 159.32185.24 219.32 BF 45.32 39.43 70.09

TABLE 3 [Variable distance data] W M T W M T Short Short Short InfinityInfinity Infinity distant distant distant d5 2.881 37.560 65.654 2.88137.560 65.654 d10 29.543 26.683 2.000 29.543 26.683 2.000 d21 5.0025.002 5.002 5.295 5.470 5.772 d24 15.836 15.836 15.836 15.543 15.36815.066

TABLE 4 [Lens group data] Group Starting surface f G1 1 146.976 G2 6−31.771 G3 11 38.664

TABLE 5 [Conditional expression corresponding value] Conditionalexpression (1)n1P/n1N = 0.903 Conditional expression (2)f1/(−f2) = 4.626Conditional expression (3)nFP/nFN = 1.031 Conditional expression(4)νFP/νFN = 0.635

FIGS. 2A, 2B, and 2C are graphs showing various aberrations of the zoomoptical system according to Example 1 upon focusing on infinity,respectively in the wide angle end state, the intermediate focal lengthstate, and the telephoto end state.

FIGS. 3A, 3B, and 3C are graphs showing various aberrations of the zoomoptical system according to Example 1 upon focusing on a short distantobject, respectively in the wide angle end state, the intermediate focallength state, and the telephoto end state.

In the aberration graphs in FIGS. 2A-2C and FIGS. 3A-3C, FNO denotes anF number, NA denotes the number of apertures, and Y denotes an imageheight. The spherical aberration graphs illustrate an F number or thenumber of apertures corresponding to the maximum aperture, astigmatismaberration graphs and distortion aberration graphs illustrate themaximum image height, and coma aberration graphs illustrate values ofimage heights. d denotes a d line (λ=587.6 nm) and g denotes a g line(λ=435.8 nm). In the astigmatism aberration graphs, a solid linerepresents a sagittal image surface, and a broken line represents ameridional image surface. In aberration graphs in Examples describedbelow, the same reference signs as in this Example are used, and aredundant description is omitted.

It can be seen in these aberration graphs that the zoom optical systemaccording to this Example can achieve excellent imaging performance withvarious aberrations successfully corrected from the wide angle end stateto the telephoto end state, and can achieve excellent imagingperformance upon focusing on a short distant object.

Example 2

Example 2 is described with reference to FIG. 4, FIGS. 5A-5C, and FIGS.6A-6C and Table 6 to Table 10. FIG. 4 is a diagram illustrating a lensconfiguration of a zoom optical system according to Example 2 of thepresent embodiment. The zoom optical system ZL(2) according to Example 2consists of, in order from an object: a first lens group G1 havingpositive refractive power; a second lens group G2 having negativerefractive power; and a third lens group G3 having positive refractivepower. In this Example, the third lens group G3 forms the subsequentgroup GR. The aperture stop S is provided in the third lens group G3,and the image surface I is disposed to the image side of the third lensgroup G3.

The first lens group G1 consists of, in order from the object, apositive lens L11 having a biconvex shape and a cemented positive lensconsisting of a negative meniscus lens L12 having a convex surfacefacing the object and a positive meniscus lens L13 having a convexsurface facing the object.

The second lens group G2 consists of, in order from the object, acemented negative lens consisting of a negative lens L21 having abiconcave shape and a positive meniscus lens L22 having a convex surfacefacing the object and a negative meniscus lens L23 having a concavesurface facing the object.

The third lens group G3 consists of, in order from the object, apositive lens L31 having a biconvex shape, a cemented positive lensconsisting of a positive lens L32 having a biconvex shape and a negativelens L33 having a biconcave shape, the aperture stop S, a cementedpositive lens consisting of a negative meniscus lens L34 having a convexsurface facing the object and a positive lens L35 having a biconvexshape, a positive meniscus lens L36 having a convex surface facing theobject, a cemented negative lens consisting of a positive meniscus lensL37 having a concave surface facing the object and a negative lens L38having a biconcave shape, and a positive meniscus lens L39 having aconvex surface facing the object.

In the optical system according to Example 2, the cemented negative lensconsisting of the positive meniscus lens L37 and the negative lens L38in the third lens group G3 (subsequent group GR) moves toward the imagesurface upon focusing from a long distant object to a short distantobject. In this Example, the second lens group G2 preferably serves as avibration-proof lens group, with a displacement component in a directionorthogonal to the optical axis, to be in charge of image blur correctionon the image surface I (image stabilization, camera shake correction).

Table 6 to Table 10 below list specification values of the opticalsystem according to Example 2.

TABLE 6 [Lens specifications] Surface number R D nd νd Object surface ∞1 107.1938 5.550 1.51680 63.88 2 −530.9538 0.322 3 117.7624 1.5001.62004 36.40 4 44.0268 7.567 1.51680 63.88 5 227.1507 Variable 6−203.0102 1.000 1.69680 55.52 7 21.2424 3.233 1.80518 25.45 8 48.81692.543 9 −42.1537 1.000 1.69680 55.52 10 −6934.7369 Variable 11 47.32753.788 1.58913 61.22 12 −85.5332 0.200 13 32.0277 4.717 1.58913 61.22 14−50.8314 1.000 1.80100 34.92 15 86.4846 2.418 16 ∞ 7.395 (Aperture stopS) 17 45.5887 1.000 1.80100 34.92 18 16.4065 5.108 1.48749 70.31 19−171.1242 0.227 20 27.3017 2.684 1.62004 36.40 21 74.0712 Variable 22−111.4238 3.422 1.62004 36.40 23 −15.5060 1.000 1.56883 56.00 24 21.5605Variable 25 44.9067 2.022 1.54814 45.79 26 69.6291 BF Image surface ∞

TABLE 7 [Various data] Zooming rate 4.23 W M T f 69.5 100.0 294.0 FNO4.68 4.68 6.21 2ω 23.36 16.00 5.46 Ymax 14.25 14.25 14.25 TL 160.38185.15 220.32 BF 38.70 38.69 64.27

TABLE 8 [Variable distance data] W M T W M T Short Short Short InfinityInfinity Infinity distant distant distant d5 10.321 39.610 72.692 10.32139.610 72.692 d10 29.998 25.487 2.000 29.998 25.487 2.000 d21 3.5653.565 3.565 3.887 4.029 4.416 d24 20.100 20.100 20.100 19.778 19.63619.249

TABLE 9 [Lens group data] Group Starting surface f G1 1 152.555 G2 6−31.420 G3 11 38.702

TABLE 10 [Conditional expression corresponding value] Conditionalexpression (1)n1P/n1N = 0.936 Conditional expression (2)f1/(−f2) = 4.855Conditional expression (3)nFP/nFN = 1.033 Conditional expression(4)νFP/νFN = 0.650

FIGS. 5A, 5B, and 5C are graphs showing various aberrations of the zoomoptical system according to Example 2 upon focusing on infinity,respectively in the wide angle end state, the intermediate focal lengthstate, and the telephoto end state. FIGS. 6A, 6B, and 6C are graphsshowing various aberrations of the zoom optical system according toExample 2 upon focusing on a short distant object, respectively in thewide angle end state, the intermediate focal length state, and thetelephoto end state. It can be seen in these aberration graphs that thezoom optical system according to this Example can achieve excellentimaging performance with various aberrations successfully corrected fromthe wide angle end state to the telephoto end state, and can achieveexcellent imaging performance upon focusing on a short distant object.

Example 3

Example 3 is described with reference to FIG. 7, FIGS. 8A-8C, and FIGS.9A-9C and Table 11 to Table 15. FIG. 7 is a diagram illustrating a lensconfiguration of a zoom optical system according to Example 3 of thepresent embodiment. The zoom optical system ZL(3) according to Example 3consists of, in order from the object: a first lens group G1 havingpositive refractive power; a second lens group G2 having negativerefractive power; a third lens group G3 having positive refractivepower; a fourth lens group G4 having negative refractive power; and afifth lens group G5 having positive refractive power. In this Example,the third to the fifth lens groups G3 to G5 form the subsequent group GRhaving positive refractive power as a whole.

The first lens group G1 consists of, in order from the object, apositive lens L11 having a biconvex shape and a cemented positive lensconsisting of a negative meniscus lens L12 having a convex surfacefacing the object and a positive meniscus lens L13 having a convexsurface facing the object.

The second lens group G2 consists of, in order from the object, acemented negative lens consisting of a negative lens L21 having abiconcave shape and a positive meniscus lens L22 having a convex surfacefacing the object and a negative lens L23 having a biconcave shape.

The third lens group G3 consists of, in order from the object, apositive lens L31 having a biconvex shape, a cemented positive lensconsisting of a positive lens L32 having a biconvex shape and a negativelens L33 having a biconcave shape, the aperture stop S, a cementedpositive lens consisting of a negative meniscus lens L34 having a convexsurface facing the object and a positive lens L35 having a biconvexshape, and a positive meniscus lens L36 having a convex surface facingthe object.

The fourth lens group G4 consists of a cemented negative lens consistingof a positive meniscus lens L41 having a concave surface facing theobject and a negative lens L42 having a biconcave shape.

The fifth lens group G5 consists of a positive meniscus lens L51 havinga convex surface facing the object.

In the optical system according to Example 3, the fourth lens group G4moves toward the image surface upon focusing from a long distant objectto a short distant object. In this Example, the second lens group G2preferably serves as a vibration-proof lens group, with a displacementcomponent in a direction orthogonal to the optical axis, to be in chargeof image blur correction on the image surface I (image stabilization,camera shake correction).

Table 11 to Table 15 below list specification values of the opticalsystem according to Example 3.

TABLE 11 [Lens specifications] Surface number R D nd νd Object surface ∞1 100.0120 5.590 1.51680 63.88 2 −356.7115 0.200 3 87.0822 1.500 1.6200436.40 4 36.8924 7.184 1.51680 63.88 5 131.1594 Variable 6 −122.14131.000 1.69680 55.52 7 20.4910 3.496 1.80518 25.45 8 49.8357 2.470 9−48.8699 1.000 1.77250 49.62 10 8360.2394 Variable 11 56.6713 3.7851.58913 61.22 12 −64.2309 0.200 13 35.4309 4.669 1.48749 70.31 14−48.4394 1.000 1.80100 34.92 15 159.7328 1.860 16 ∞ 16.684  (Aperturestop S) 17 57.8297 1.000 1.80100 34.92 18 19.6163 4.946 1.48749 70.31 19−96.4204 0.200 20 27.1066 2.717 1.62004 36.40 21 65.2029 Variable 22−157.1131 3.395 1.64769 33.73 23 −22.3553 1.000 1.56883 56.00 24 25.0407Variable 25 46.5745 2.500 1.62004 36.40 26 60.0000 BF Image surface ∞

TABLE 12 [Various data] W M T f 68.6 100.0 294.0 FNO 4.69 4.72 6.10 2ω23.74 16.04 5.46 Ymax 14.25 14.25 14.25 TL 164.32 184.76 221.32 BF 38.5238.73 64.73

TABLE 13 [Variable distance data] W M T W M T Short Short Short InfinityInfinity Infinity distant distant distant d5 4.964 31.058 63.669 4.96431.058 63.669 d10 29.909 24.050 2.000 29.909 24.050 2.000 d21 3.6664.368 2.697 4.068 4.962 3.755 d24 20.866 20.163 21.834 20.464 19.56920.776

TABLE 14 [Lens group data] Group Starting surface f G1 1 137.939 G2 6−30.083 G3 11 34.644 G4 22 −42.585 G5 25 313.363

TABLE 15 [Conditional expression corresponding value] Conditionalexpression (1)n1P/n1N = 0.936 Conditional expression (2)f1/(−f2) = 4.585Conditional expression (3)nFP/nFN = 1.050 Conditional expression(4)νFP/νFN = 0.602

FIGS. 8A, 8B, and 8C are graphs showing various aberrations of the zoomoptical system according to Example 3 upon focusing on infinity,respectively in the wide angle end state, the intermediate focal lengthstate, and the telephoto end state. FIGS. 9A, 9B, and 9C are graphsshowing various aberrations of the zoom optical system according toExample 3 upon focusing on a short distant object, respectively in thewide angle end state, the intermediate focal length state, and thetelephoto end state. It can be seen in these aberration graphs that thezoom optical system according to this Example can achieve excellentimaging performance with various aberrations successfully corrected fromthe wide angle end state to the telephoto end state, and can achieveexcellent imaging performance upon focusing on a short distant object.

Example 4

Example 4 is described with reference to FIG. 10, FIGS. 11A-11C, andFIGS. 12A-12C and Table 16 to Table 20. FIG. 10 is a diagramillustrating a lens configuration of a zoom optical system according toExample 4 of the present embodiment. The zoom optical system ZL(4)according to Example 4 consists of, in order from the object: a firstlens group G1 having positive refractive power; a second lens group G2having negative refractive power; a third lens group G3 having positiverefractive power; a fourth lens group G4 having negative refractivepower; and a fifth lens group G5 having positive refractive power. Inthis Example, the third to the fifth lens groups G3 to G5 form thesubsequent group GR having positive refractive power as a whole.

The first lens group G1 consists of, in order from the object, apositive lens L11 having a biconvex shape and a cemented positive lensconsisting of a negative meniscus lens L12 having a convex surfacefacing the object and a positive meniscus lens L13 having a convexsurface facing the object.

The second lens group G2 consists of, in order from the object, acemented negative lens consisting of a negative lens L21 having abiconcave shape and a positive meniscus lens L22 having a convex surfacefacing the object and a negative lens L23 having a biconcave shape.

The third lens group G3 consists of, in order from the object, apositive lens L31 having a biconvex shape, a cemented positive lensconsisting of a positive lens L32 having a biconvex shape and a negativelens L33 having a biconcave shape, the aperture stop S, a cementedpositive lens consisting of a negative meniscus lens L34 having a convexsurface facing the object and a positive lens L35 having a biconvexshape, and a positive meniscus lens L36 having a convex surface facingthe object.

The fourth lens group G4 consists of a cemented negative lens consistingof a positive meniscus lens L41 having a concave surface facing theobject and a negative lens L42 having a biconcave shape and a negativemeniscus lens L43 having a convex surface facing the object.

The fifth lens group G5 consists of a positive meniscus lens L51 havinga convex surface facing the object.

In the optical system according to Example 4, the fourth lens group G4moves toward the image surface upon focusing from a long distant objectto a short distant object. In this Example, the second lens group G2preferably serves as a vibration-proof lens group, with a displacementcomponent in a direction orthogonal to the optical axis, to be in chargeof image blur correction on the image surface I (image stabilization,camera shake correction).

Table 16 to Table 20 below list specification values of the opticalsystem according to Example 4.

TABLE 16 [Lens specifications] Surface number R D nd νd Object surface ∞1 102.5193 5.542 1.51680 63.88 2 −366.1796 0.200 3 90.4094 1.500 1.6200436.40 4 37.8518 7.229 1.51680 63.88 5 144.7539 Variable 6 −163.50531.000 1.69680 55.52 7 20.5835 3.475 1.80518 25.45 8 48.1602 2.598 9−47.4086 1.000 1.77250 49.62 10 4634.3570 Variable 11 57.6094 3.8431.58913 61.22 12 −66.7307 0.200 13 36.4629 4.709 1.48749 70.31 14−48.7603 1.000 1.80100 34.92 15 206.1449 1.786 16 ∞ 16.497  (Aperturestop S) 17 55.1101 1.000 1.80100 34.92 18 19.3181 4.785 1.48749 70.31 19−100.3387 0.200 20 26.0254 2.707 1.62004 36.40 21 57.5286 Variable 22−201.9970 3.376 1.64769 33.73 23 −22.7237 1.000 1.56883 56.00 24 29.22951.172 25 34.9681 1.000 1.79952 42.09 26 26.1166 Variable 27 39.94392.135 1.62004 36.40 28 60.0000 BF Image surface ∞

TABLE 17 [Various data] Zooming rate 4.28 W M T f 68.7 100.0 294.0 FNO4.70 4.73 6.06 2ω 23.74 16.08 5.48 Ymax 14.25 14.25 14.25 TL 164.32184.47 221.32 BF 38.52 38.72 64.52

TABLE 18 [Variable distance data] W M T W M T Short Short Short InfinityInfinity Infinity distant distant distant d5 4.000 30.052 63.492 4.00030.052 63.492 d10 30.492 24.393 2.000 30.492 24.393 2.000 d21 3.6864.454 2.923 4.052 4.994 3.907 d26 19.668 18.899 20.430 19.301 18.35919.446

TABLE 19 [Lens group data] Group Starting surface f G1 1 138.289 G2 6−30.436 G3 11 34.256 G4 22 −36.764 G5 27 185.180

TABLE 20 [Conditional expression corresponding value] Conditionalexpression(1) n1P/n1N = 0.936 Conditional expression(2) f1/(−f2) = 4.544Conditional expression(3) nFP/nFN = 1.050 Conditional expression(4)νFP/νFN = 0.602

FIGS. 11A, 11B, and 11C are graphs showing various aberrations of thezoom optical system according to Example 4 upon focusing on infinity,respectively in the wide angle end state, the intermediate focal lengthstate, and the telephoto end state. FIGS. 12A, 12B, and 12C are graphsshowing various aberrations of the zoom optical system according toExample 4 upon focusing on a short distant object, respectively in thewide angle end state, the intermediate focal length state, and thetelephoto end state. It can be seen in these aberration graphs that thezoom optical system according to this Example can achieve excellentimaging performance with various aberrations successfully corrected fromthe wide angle end state to the telephoto end state, and can achieveexcellent imaging performance upon focusing on a short distant object.

Furthermore, according to Examples described above, the focus lens groupis small and light weight so that quick and quiet AF can be implementedwithout using a large barrel. Furthermore, a zoom optical systemsuccessfully preventing variation of aberrations upon zooming from thewide angle end state to the telephoto end state, as well as variation ofaberrations upon focusing can be implemented.

Examples described above are merely examples of the invention accordingto the present embodiment. The invention according to the presentembodiment is not limited to these examples.

The following configurations can be appropriately employed as long asthe optical performance of the zoom optical system according to thepresent embodiment is not compromised.

Examples of values of the zoom optical system according the presentembodiment having three or five lens groups are described above.However, this should not be construed in a limiting sense, and a zoomoptical system with other lens group configurations (for example, aconfiguration with four or six lens groups or the like) may be employed.More specifically, the zoom optical system according to the presentembodiment may be further provided with a lens or a lens group closestto an object or further provided with a lens or a lens group closest tothe image surface. The lens group is a portion including at least onelens separated from another lens with a distance varying upon zooming.

The focusing group is a portion including at least one lens separatedfrom another lens with a distance varying upon focusing. Specifically,the focusing group may be provided for focusing, with a single or aplurality of lens groups or a partial lens group moved in the opticalaxis direction. The focusing group can be applied to auto focus, and issuitable for motor driving for auto focus (using supersonic wave motors,etc.).

The lens surface maybe formed to have a spherical surface or a planersurface, or may be formed to have an aspherical shape. The lens surfacehaving a spherical surface or a planer surface features easy lensprocessing and assembly adjustment, which leads to the processing andassembly adjustment less likely to involve an error compromising theoptical performance, and thus is preferable. Furthermore, there is anadvantage that a rendering performance is not largely compromised evenwhen the image surface is displaced.

The lens surface having an aspherical shape may be achieved with any oneof an aspherical shape formed by grinding, a glass-molded asphericalshape obtained by molding a glass piece into an aspherical shape, and acomposite type aspherical surface obtained by providing an asphericalshape resin piece on a glass surface. A lens surface may be adiffractive surface. The lens may be a gradient index lens (GRIN lens)or a plastic lens.

The aperture stop is preferably disposed in the neighborhood of orwithin the third lens group. Alternatively, a lens frame may serve asthe aperture stop so that the member serving as the aperture stop needsnot to be provided.

The lens surfaces may be provided with an antireflection film featuringhigh transmittance over a wide range of wavelengths to achieve anexcellent optical performance with reduced flare and ghosting andincreased contrast. Thus, an excellent optical performance with reducedflare and ghosting and increased contrast can be achieved.

EXPLANATION OF NUMERALS AND CHARACTERS G1 first lens group G2 secondlens group G3 third lens group G4 fourth lens group G5 fifth lens groupGR subsequent group I image surface S aperture stop

1. A zoom optical system comprising, in order from an object: a firstlens group having positive refractive power; a second lens group havingnegative refractive power; and a subsequent group including at least onelens group, wherein upon zooming, distances between the first lens groupand the second lens group and between the second lens group and thesubsequent group change, the subsequent group comprises a focusing grouphaving negative refractive power for focusing, the first lens groupcomprises a 1-1st lens having positive refractive power and is disposedclosest to the object, and a following conditional expression issatisfied:0.85<n1P/n1N<1.00 where, n1P denotes a refractive index of a lens withlargest positive refractive power in the first lens group, and n1Ndenotes a refractive index of a lens with largest negative refractivepower in the first lens group.
 2. The zoom optical system according toclaim 1, wherein a following conditional expression is satisfied:4.30<f1/(−f2)<5.00 where, f1 denotes a focal length of the first lensgroup, and f2 denotes a focal length of the second lens group.
 3. Thezoom optical system according to claim 1, wherein the first lens groupmoves toward the object upon zooming from a wide angle end state to atelephoto end state.
 4. The zoom optical system according to claim 1,wherein the focusing group comprises at least one lens having positiverefractive power and at least one lens having negative refractive power.5. The zoom optical system according to claim 4, wherein a followingconditional expression is satisfied:1.00<nFP/nFN<1.20 where, nFP denotes a refractive index of a lens withlargest positive refractive power in the focusing group, and nFN denotesa refractive index of a lens with largest negative refractive power inthe focusing group.
 6. The zoom optical system according to claim 4,wherein a following conditional expression is satisfied:0.52<νFP/νFN<0.82 where, νFP denotes an Abbe number of the lens with thelargest positive refractive power in the focusing group, and νFN denotesan Abbe number of the lens with the largest negative refractive power inthe focusing group.
 7. The zoom optical system according to claim 1,wherein the first lens group comprises, in order from the object: the1-1st lens; a 1-2nd lens having negative refractive power; and a 1-3rdlens having positive refractive power.
 8. The zoom optical systemaccording to claim 1, wherein the second lens group comprises, in orderfrom the object: a 2-1st lens having negative refractive power; a 2-2ndlens having positive refractive power; and a 2-3rd lens having negativerefractive power.
 9. An optical apparatus comprising the zoom opticalsystem according to claim
 1. 10. A method for manufacturing a zoomoptical system which comprises, in order from an object: a first lensgroup having positive refractive power; a second lens group havingnegative refractive power; and a subsequent group including at least onelens group, the method comprising a step of arranging the lens groups ina lens barrel so that: upon zooming, distances between the first lensgroup and the second lens group and between the second lens group andthe subsequent group change, the subsequent group comprises a focusinggroup having negative refractive power for focusing, the first lensgroup comprises a 1-1st lens having positive refractive power and isdisposed closest to the object in the first lens group, and a followingconditional expression is satisfied:0.85<n1P/n1N<1.00 where, n1P denotes a refractive index of a lens withlargest positive refractive power in the first lens group, and n1Ndenotes a refractive index of a lens with largest negative refractivepower in the first lens group.